4 years, 2 months and 15 days
by Tako Phin
Summary: "Which one do you actually prefer, us as doubles partner or singles?" The middle schooler Inui asked the elementary student Yanagi.


**AN: Written to celebrate Data Pair's birthday (Inui on 3rd June and Yanagi on 4th June). Happy birthday you two endearing complicated characters!**

* * *

"Let's go, Sadaharu. Prepare yourself." Yanagi said, his hand stretched out holding the green ball towards the person at the other end of the court. Yanagi had never considered Inui to be his opponent, never in the past, and definitely not in the present, even if this was the decisive match to Rikkai's third consecutive victory. It was and had always been a friendly spar, a test of strength.

"I will never lose." Inui countered, because that was what exactly how his younger self had answered before. That was inaccurate. During those 4 years, 2 months and 15 days, Inui had lost to a number of people: Tezuka, Echizen, and Hyoutei's Shishido-Ootori pair. _I will not lose to you, Renji_.

xxx

"I will never lose." Right after the eleven year old Inui said that, something seemed to change. He was still standing on his own two feet, holding his racquet with both hands. His doubles partner Yanagi was still standing across him. But he saw no net, and the green court they had been playing on was replaced with grey concrete.

The first thing Yanagi noticed was how the warm evening wind around him suddenly turned stagnant.

Inui also noted how the orange sky had miraculously turned blue. He began mentally listing down all the possible explanation for this: bizarre weather phenomenon (0.1%), dream (89%), or hallucination (9.9%). Then Inui began tracing back his memories to figure out what he could have done to be seeing things, starting from when he woke up this morning at 6.14am.

Teleportation or time travel, or both? Before Yanagi could decide on an answer, a new piece of puzzle appeared.

"Renji, from here on there is no data, let's finish this!" Someone exclaimed loudly.

Yanagi snapped his eyes open at Inui whom he thought had said those words. However, his partner returned his stare with equally confused look. That had to be Inui's voice, Yanagi was certain, though it was rougher and deeper.

"I'll make you eat those words, Sadaharu!"

It was Inui's turn to stare at Yanagi whom he thought to be the one to say that sentence. The words 'data', 'Renji' and 'Sadaharu' used in a conversation…it was too much to be a coincidence.

A firm sound of smacking caused the two elementary school students to turned their head to the source. The smacking sound continued, almost forming a consistent beat. Definitely the sound of tennis ball being rallied back and forth, Inui concluded. They could not see anything from where they were standing, given their height on top of the crowd gathered along the edges that blocked their vision.

Yanagi was the first to make his move. He silently walked away from Inui, towards a space where the railings were not crowded. Inui ran to join him.

They stood behind the railings that was almost as tall as they were, peeking at the ongoing tennis match below through the gaps in the structure. The player wearing yellow looked similar to Yanagi with his perpetually closed eyes, but his hair was cut into a short bob and he was clearly older and taller. Besides the height, the one wearing blue and white looked _exactly_ like Inui, right from the shape of the glasses to the hairstyle.

"Are those..?" Inui wasn't sure how to phrase his question. Yanagi was glad that his partner did not, for he would not know how to answer.

"Game Inui, 6-5!"

Yanagi tried not to mull over the score. This situation at hand was of greater importance. "That's definitely you, hakase." Yanagi pointed out instead,

Inui stared even more intently at the two players on the court. He scrutinized how the blue and white player served and how he returned the shots. Inui was sure he was using data tennis. All the evidences supported what his partner had deducted.

"Game Yanagi, game count, 6-6."

It was only Sadaharu and Renji before. Unless these two people happen to have the same name, physical characteristics, and tennis play style, Inui was convinced that they were staring at their older selves, as absurd as this notion might seem. "99% probability that's also you, kyouju." Inui turned to his partner.

"99?"

"1% because of the hair." Inui explained. And the fact that they were playing _against_ each other in an official match, but Inui did not say that out loud.

Suddenly Inui pinched his own cheek. Yanagi stared at his friend's odd gesture and refrained from making any comment. Then, wordlessly Yanagi brought his hand to his cheek and did the same to himself. Now his cheek was throbbing uncomfortably and he was still seeing their adult selves engaged in an abnormally long rally.

Inui rubbed his reddened cheek soothingly. "Well, that settles it." Inui spun on his heels and planned to ask around for more information.

"Wait." Yanagi called out before Inui walked away. "We don't belong to this timeline. Don't do unnecessary things." Yanagi advised. He wished he had understood those time travel theories he had found during one of his visits to the library more.

Inui was equally clueless, but he trusted his friend's judgement so he stayed and continued to observe the tie-breaker that was still ongoing. Yanagi looked very absorbed in the match. Inui, too, was admittedly curious as to the outcome of the match. Who was stronger between the two of them in the future?

"Game set won by Inui, 7-6"

The younger Inui gaped in awe. It was a close fight, with the tie breaker ending at 31-29. Yanagi did not show any visible reaction, but being Inui's partner for years, Inui could spot the slight frown on his face.

"I…lost?" The young Yanagi heard his older self said. So his suspicions were correct after all, one that he would soon gamble their partnership on. A foreign feeling gripped him instead of the usual thrill that came whenever he had his analysis confirmed. Perhaps it had something to do with him being in the future, Yanagi reasoned as he clutched his aching chest.

"Something wrong?" The younger Inui asked concernedly. Yanagi shook his head and turned to look at their future selves, hoping that Inui would follow suit. Inui did.

"It was all by chance. The chances of winning were 50/50. The next time we play, the winner might be you instead, Renji." The older Inui replied.

"Fuu…I guess this means you've increased your data again."

"The same goes for you."

Their future selves returned to their respective teams. While the older Inui was greeted with cheers from his teammates, the older Yanagi was standing solemnly before a scary looking guy with a cap.

"Kyouju." The younger Inui called out his partner. "Shall we try asking our future selves?"

"I've told you Hakase," Yanagi turned to face Inui. "Don't do unnecessary things."

"The probability of us getting out of this on our own is a mere 0.2%, kyouju. I believe it's necessary to seek help, and our future selves should be able to do that best." Inui debated.

"Hakase…" Yanagi wanted to insist that they shouldn't, but he did not have sufficient evidence to debate against his partner. The only thing he understood about multiple timeline was the concept of chain reaction, that their actions could alter the timeline, which Yanagi was not even certain if it was applicable here.

"Let's go, kyouju." Inui was dragging Yanagi away by his arm. Yanagi couldn't find the strength to resist.

A sudden loud slap froze them both on the spot. There was something off with the sound, Yanagi realized. It did not sound like a typical hit to a flesh, but more of an unusual object hitting a racquet. Both of them turned their heads to the court below to find the answer.

The older Yanagi was nearly slapped by the scary guy in the cap if not for the messy black haired boy intervening with his racquet.

Inui dashed closer to the railings, leaning over it dangerously as if he was about to jump. The steel structure rattled at the force Inui clutched it with. "Hakase!" Yanagi warned.

"That guy with the cap is going to beat you up." Inui reasoned, his voice oddly calm in contrast to his trembling grip.

"I'm here." Yanagi countered. "I'm safe. That's my future self. Let him handle it."

"Kyouju." Inui let go of one hand from the railings and turned to face Yanagi. "Don't do unnecessary things, I get that. But I'm not going to stand here and watch my friend get beaten up, no matter whether it's the older version or not."

"Don't be unreasonable, hakase!" Yanagi's voice was louder than before.

The two young players continued to debate heatedly, unaware that someone was observing them right below where they were standing.

"What's so interesting there nyaa? You've been staring up-…" Kikumaru sprang up to where Inui had been standing still for some time and looking in the same direction. He saw two young boys bickering, one of them looked suspiciously similar to Inui. "Nyaa Inui, you bring your younger brother here?"

"Inui has a younger brother?" Oishi joined the conversation from his seat on the spectators area across them. Inui did not seem to have heard them. He was completely frozen, standing perfectly straight with his head titled up. Kikumaru wondered what was so interesting about the two boys when all he could hear was 'hakase' and 'kyouju'.

"Nyaa? Earth to Inui?"

Finally Inui defrosted. Fixing his glasses, he lowered his head to Oishi. "I'm really sorry for the bad timing, but I must excuse myself." Inui said curtly and walked away.

"But the match-!" Kikumaru called out, flickering his gaze worriedly at Inui's figure that gradually grew farther and Fuji who was determining the first serve with his opponent. "Oishi!" Kikumaru yelped, not knowing what to do.

"It's okay, Eiji." Oishi assured him. "It looks like it's very important. Inui has done very well on his part anyway."

Someone seated on the spectators area opposite to them was observing the entire exchange closely. The hands that were resting on his thighs clenched into tight fists. Was it mere coincidence that the two kids bear very precise physical resemblance to both Inui and himself four years ago, even right down to their jersey and their racquets? Hallucination would be another possibility, but Yanagi had endured far worse physical exertions under Rikkaidai's training regime that his mental fortitude should be stronger than that.

He saw Inui walked away from his team and his fists began to tremble slightly. He glanced at the court, at his junior who had to play his match because Yanagi had lost his. Then he glanced at the back of his vice captain who was seated on the bench, and he recalled their blue haired captain who should have been there instead, their hospitalized captain that would be expecting their arrival with the golden trophy. Yanagi clenched his shaking fists around the fabric of his shorts, his head bowed in silent apology.

xxx

"Sadaharu!" The younger Yanagi shouted, grabbing onto the sleeve of Inui's jersey to hold him back. "Listen to me. Whatever happens in this timeline should not be any of our concern. We need to focus on returning to our timeline."

"That's why I'll go and ask our future selves. I don't know anything about time travel. The probability of you knowing anything more than our future selves is nil, Renji." Inui countered. "We'll bring them to somewhere isolated to avoid the unnecessary actions you've been mentioning."

"That in itself in unnecessary." Yanagi was growing more and more frustrated. Why couldn't his partner understand?

"The probability that Inui Sadaharu's plan will work is 89%."

The younger Yanagi shot a glare at his partner, but Inui was not looking at him. He was looking over his shoulder to the person towering behind him. It was the older Inui who had spoken.

Yanagi's first instinct was to spin on his heel and run as fast as he could in the opposite direction.

"You're thinking of running away under the pretense of minimizing your influence in this alternate timeline, am I correct?"

And the younger Yanagi would have done exactly that, if not for the voice that stopped him before he could do so. If the older Inui was standing behind the younger Inui, the person behind him had to be none other than his older self, the only person that could unmask Yanagi's thoughts like it was his own.

The younger Inui sensed his partner's discomfort at the situation. This was the situation that he had wanted, but not his partner. Three on one was rather unfair too. "Do we know each other?" The younger Inui tried with a slight stutter. Acting was never his forte.

"The two of you are from Midorigawa First Elementary School, right?" The older Inui said in a manner that made it seemed more like a statement rather than a question.

At least the younger Inui could manage a shake of his head, albeit hesitantly. The younger Yanagi was frozen still, unresponsive to the ongoing conversation. Inui doubted he could maintain this whole charade on his own. All they had to ask was ' _What's your name?_ '.

Their future selves took a more unique route to end it. "Mitsuya Akuto." The older Yanagi said out of nowhere. The name was foreign to Inui's ears, but the younger Yanagi jerked and snapped his head at his older self in response. Inui understood then that his partner had just failed the test.

"Shall I do the same?" Inui's future self asked. The younger one shook his head. He was more than relieved to end this whole thing anyway. Though it still worried him to see his partner losing his usual calm composure.

A cackling shriek accompanied by frantic sound of shots filled the background. The younger Inui took a peek at the ongoing match at the courts below them and shivered at what he saw. "Do you…senpais mind if we move somewhere else to discuss this?" Inui asked, not sure how to address their future selves.

The older Inui agreed with his suggestion. The older Yanagi seemed somewhat hesitant in agreeing, but followed anyway as the older Inui led them to somewhere away from the match, ushering the younger Yanagi to do the same by walking behind him.

The younger ones stood next to each other, facing their older selves respectively. The younger Inui initiated the conversation by explaining in as much detail as possible what he could remember before they were teleported here.

"And about two minutes and ten seconds later, the two of you exclaimed, in your exact words, 'Renji, from here on there is no data, let's finish this!' and 'I'll make you eat those words, Sadaharu!'" The younger Inui tried to mimic the older selves' lower voice while quoting them.

"Then the two of you must have appeared when we reach _that_ point." The older Inui suggested.

"The score was 5-4 to your favor, correct?" The older Yanagi gestured to his younger self, who gave a slight nod in affirmation.

"The probability that our recreation of the match 4 years, 2 months and 15 days has triggered an overlap in the two timelines which lead to this is 89%" The older Inui calculated.

"Then, the same event should be able to reverse the situation." The older Yanagi continued.

Before they could discuss this solution further, the younger boys spotted a mass of people in yellow jersey similar to the one the older Yanagi was wearing walking towards them. A total of 5 people, the younger Inui counted. The younger Yanagi felt a sense of urgency, a huge uneasiness from them.

The older Yanagi turned to face his team and spotted their youngest regular sulking. "Don't tell me…"

"I'll tell you. Our baby lost, 5-7." Niou patted Kirihara's head who did not even try to shrug him off as per usual. "Sanada's now playing against Seigaku's freshman. He told us to go ahead."

Yagyuu titled his head upon seeing Inui and Yanagi and what seemed to be their younger counterparts. "Are we perhaps interrupting a family reunion?"

Yanagi spared a glance at the two younger boys for several seconds. "No." He replied and walked to join his team. "I'll be back to settle this."

"Wait, Renji." The older Inui called out. Bending down slightly, he placed his hand on the younger Inui's back and pushed him towards the Rikkaidai members. "Take him with you."

Both Yanagis and the younger Inui stared questioningly at the older Inui. "The probability of you having a more effective-"

"I get it, Sadaharu." The older Yanagi nodded his head at the younger Inui, gesturing for him to follow as the crowd continued to walk at a brisk pace. The younger Inui glanced at his partner, who gave him a reassuring nod in return. Soon it was only the older Inui and the younger Yanagi left in the place.

"That's unexpected." The older Inui stated after the crowd was no longer within their range of vision. "The probability of you rejecting this suggestion was 79%."

"Which is exactly why I chose to stay." The younger Yanagi replied curtly.

xxx

Yanagi was slightly grateful that his teammates were too occupied with either their captain's operation or the decisive single match their vice captain was fiercely engaged in that none had asked him about the little Inui tagging along. Once they had reached the hospital, Yanagi quickly excused both himself and the little Inui to the rooftop. He did not need another set of problem to worry about.

"Kyouj- no. Yanagi-senpai?"

"Where would you like me to begin?" Yanagi immediately asked. He knew how curious his childhood friend could get, especially at that age. That was the main reason he got him away from his team before too much information was leaked.

The younger Inui stared at Yanagi, contemplating his answer. His first question was something that Yanagi had hoped to never escape those lips.

"Why is my future self playing against you? Aren't we doubles partner?"

xxx

Instead of going back to his team, Inui took the younger Yanagi closer to the railings. He was rightfully curious of this unpredictable match, especially when it was the first time they had gotten this far in the regionals. That was distracting Inui enough from properly figuring out a solution to this. He pitied Yanagi, who undoubtedly had it worse.

Inui realized that it was actually easier to figure out what the older Yanagi was thinking as compared to the younger one. The younger Yanagi was more peculiar in his way of thinking. It was less…logical, yet at the same time Inui was sure there was a perfectly logical explanation for everything that Yanagi did. For one, the younger Yanagi had persistently insisted on not interfering with the current timeline, yet he was content on letting the younger Inui go alone.

Inui could only give a 67% prediction that the younger Yanagi was trying his best to 'not do unnecessary things' as he had said, having asked nothing so far and opting to stare at the ongoing match instead.

"Let me ask you a question, kyouju." Inui said without averting his gaze from the match. This question had always been bugging at the back of his head ever since that day. No matter how much Inui tried to analyze it, the probability never reached beyond 60%. He could not ask the older Yanagi this, and though he doubted the younger one would bother to answer him, it would not hurt to ask.

"Which one do you actually prefer, us as doubles partner or singles?"

The younger Yanagi was clearly taken aback by the question, though he tried to keep it as much as possible to himself.

"And just to clarify, your actions in this timeline should not be of much significance to the overall balance. Don't worry, and instead take this opportunity as a chance to learn more about each other." Inui added, though it clearly did nothing to placate the younger Yanagi.

xxx

Inui stared at the older Yanagi. Unlike his younger counterpart, it was more difficult to read his expression. Since they were taking a detour from solving this time travel chaos, Inui might as well take the opportunity to gather information from the future. Since his arrival in this future timeline about an hour and ten minutes ago, there were so many things that Inui wanted to ask about, like _why did that cap wearing guy tried to hit you?_ or _why are we in the hospital instead of watching the match?_ or even _why did you cut your hair?_

Most importantly, why did they end up in different schools? Inui had not heard anything from Yanagi about moving away, and he himself was definitely not moving away. They had promised to be doubles partner forever when they had won in Hawaii. Of course, Inui knew nothing was eternal, and they bound to stop playing tennis altogether eventually, thus defying that promise. But he did not expect them to be rivals.

They were standing near the tall fence that protected people from accidentally falling from the tall height on the rooftop. The sudden rattling noise made when Yanagi's fingers latched through the diamond pattern of the fence startled Inui. Other than that, the older Yanagi was silent.

"As my younger self has said, don't do anything unnecessary." Yanagi replied.

Inui had only opened his mouth to protest before Yanagi continued. "The answer shall be revealed to you shortly in your own timeline. The knowledge is unnecessary to you at this point in time."

Inui was not going down without a fight. "What happened? Did you move away? Did we have a fight? Did we disagree on choosing middle school?" He persistently asked.

"No matter how many times you ask, I will not tell you the answer." the older Yanagi stated in a manner that gave no leeway to continue the conversation. The younger Inui pouted. He hated it when his partner became that secretive. There was just no way for Inui to pass through that wall, nothing he could do other than to wait for Yanagi to pull it down himself. It was apparently a trait that Yanagi never grew out from, as Inui had just discovered.

"There is something that I can tell you." Yanagi suddenly said much to Inui's surprise. That's a whole new record, twenty one seconds.

"Whatever happens when you return, do not forget what you have seen here. Do not try to oppose it. Don't waste your time, for-"

The older Yanagi halted abruptly. When the younger Inui glanced to check on him, he found that the older man was looking at the entrance to the rooftop instead. Inui did not notice someone had joined them. It was one of his teammates they had gone together with before, the bald one, standing at the door frame.

"Yanagi…"

That was all the bald man needed to say for Yanagi to understand the situation. "Let's go back." Yanagi said to Inui, his voice was soft. He began walking out of the rooftop past his teammate, not bothering to check whether Inui followed him or not.

Inui trailed behind, giving themselves a distance of two steps.

xxx

This was the future, the younger Yanagi told himself. He was growing to hate it by the minute.

His future self had lost against Inui's future self. Now as a result, his team lost against Inui's team. He knew he should be glad for Inui- and he was, really. It was a living proof that what he did, leaving Inui without farewell, was a justified move.

The older Inui had left him temporarily to celebrate with his team. From where he was standing, he could see the older man cheering down below, throwing the player that had just won his match up in the air with his teammates.

This was for the better. He did not have to answer Inui's questions this way.

"Remember that this is the future. I have data on what you will do for the next 4 years, 2 months and 15 days. " Inui had told him. It had not really registered in Yanagi's mind that this older Inui knew that Yanagi was going to break their partnership tomorrow. But it should not matter, for it worked out in Inui's benefit in the end. He was quite confident that his older self would not reveal this to the younger Inui for that same reason.

But…What if they had stayed together? What if Yanagi had told Inui about it? Inui might decide to move together with him, and they would still be playing doubles together. Perhaps they would be able to reach the top together, instead of what was happening now...

That would be unfair to his partner, Yanagi reprimanded himself. He was the reason why Inui was not able to develop his skill to its highest potential. He was holding him back for his own benefit.

Before the older Inui left to gather with his team, he had told Yanagi, "I might be better as a singles player, but I prefer doubles, actually."

"Me too." The younger Yanagi said to the wind, letting it carry his voice away to a place that would never reach anyone's ears.

xxx

The older Inui did not return alone. He was back at the same time the older Yanagi and the younger Inui returned from their trip. The older men were engaged in a serious discussion as they walked towards where the younger Yanagi was standing.

"So this is the plan we've come up with." The older Inui began explaining the details of what they were about to do. While the younger Yanagi absorbed all the details, he wondered what the older Yanagi had talked about with the younger Inui. His partner was looking at him with a slightly curious face. He supposed the older Yanagi might have hinted him about the moving.

The plan involved them playing a match against each other simultaneously, replicating how the game had progressed between the younger ones exactly up until 5-4. The older ones would be playing against the younger ones to control the flow of the game. It was rather exciting, the younger Inui thought, to be able to gather data on how the older Yanagi played beyond what he had already seen. At the same time, he was rather worried to go back to his own timeline. It was one thing to predict the future, it was another thing to have the future shown to you.

"Before we begin, I'd like to talk to my younger counterpart for a moment." The older Inui said, placing a hand on the younger Inui's spiky hair. "I suggest you do the same, Renji."

Thus they split in two, standing close enough that they could see each other but far enough to not have each other eavesdropping on their conversation. Both of them talked for some time before they converged back in the middle.

"Shall we begin?"

xxx

The younger Yanagi hit the ball across the court to where the older Inui was standing. He had quite a vivid recollection on how his match against hakase had gone, especially when not even a day had passed. The older Inui was also accurately returning every single shots exactly to how the younger Inui would. But Yanagi could tell his shots had more power in it, and more was released gradually as the match progressed that Yanagi nearly missed what should have been his point. He knew the potential his partner had, and it was enlightening to see how much his partner could improve in years.

 _"Is there anything you want me to do differently?"_

Inui did not need to re-read his notebook to recreate the exact match they had 4 years, 2 months and 15 days ago, or rather the one he just had 3 hours and 10 minutes ago. He made sure every shots landed in the exact same spots, returned in the exact same manner. It was easier to stick to the data with the younger Yanagi who was also returning his shots precisely according to data, though Inui was not certain whether that was deliberate or instinctual on Yanagi's part.

 _"Regardless of what would happen between you and Renji, this time, please take good care of him."_

Unlike Inui, the older Yanagi was not sticking very closely to how the match had progressed four years ago. As long as the accumulation of the points tallied, Yanagi was more than willing to allow the younger Inui to try and defeat him. He even deliberately demonstrated moves that his younger self had not learnt yet for both youngsters to see.

 _"When you reach this point once again, when you and Sadaharu face each other next time,_ ** _win_** _."_

The younger Inui was less bothered with remembering how his match with kyouju had progressed earlier, and thankfully neither was the older Yanagi. So Inui took this opportunity to test his strength against the older Yanagi instead, trying to win what should have been his points earnestly while taking note of the new moves that Yanagi had picked up over the years.

This had to be the only time when he wished he, and all of them, were not such pragmatic people. There were so much things they could have talked about, that they could learn from each other. It would not hurt to spend an entire day here in return for informations that could be used to better the future.

That was just who they were. Plenty of data could be gathered through conversations, but the untold held unlimited information, infinite possibilities.

 _"I'll make sure to advance without regrets."_

 _"_ Let's go, Sadaharu. Prepare yourself." Both Yanagi said, holding out the ball towards Inui.

"I will never lose." Both Inui answered, standing with both hands holding the racquet, ready to accept Yanagi's serve.

The serve never arrived. There was no opponent for Yanagi to serve to, and there was no opponent serving the ball to Inui. Both Inui and Yanagi dropped their forms and looked at each other. They smiled.

 _Until we meet again in 4 years, 2 months and 15 days._


End file.
